Control defrost device for refrigeration apparatus



June 21, 1966 R. H. THORNER 3,256,707

CONTROL DEFROST DEVICE FOR REFRIGERATION APPARATUS Original Filed April 5, 1961 IN V EN TOR. 205527 b. Tao/2N5? l By @0620 United States Patent 3,256,707 CUNTROL DEFRQST DEVHIE FQR REFRIG- ERATIQN APPARATUS Robert H. Thorner, 8750 W. Chicago Blvd, Detroit, Mich. tjontinuation of application Ser. No. 100,137, Apr. 3, 1961. This application July 30, 1965, Ser. No. 475,958 45 Claims. (Cl. 6214ti) This application is a continuation of my copending application No. 100,137 filed April 3, 1961, which was a continuation-in-part of my then copending application No. 43,825 filed July 19, 1960, now abandoned, which was in turn a continuation-in-part of copending application No. 480,025, filed January 5, 1955, now Patent No. 2,949,016, issued August 16, 1960.

The present invention relates primarily to a control mechanism for refrigeration apparatus and particularly to a control device for controlling the formation and reduction of ice on a cooling unit, such as for defrosting systems of refrigerator or air-conditioning apparatus. In a broader aspect, the present invention may be employed to control the thickness of formation of any substantially solid or pliable material on (or in) any solid base, such as on a tube or rod, etc., particularly when the materialformation is very slow.

In numerous refrigerating systems, means are provided to control the build up and elimination (or reduction) of ice or frost which may form on the evaporator. These systems often include heating means to remove or reduce such formation of ice. In certain types of commercial refrigeration such as ice-bank systems, as well as in some defrosting systems, such removal means comprises merely a switch to turn the compressor off so that the ambient heat eventually diminishes the ice coating on the evaporator. For purposes of this disclosure, ice and frost can be considered synonymously.

Defrosting control systems are used to remove the frost which forms in the usual evaporator coils as well as on other parts or on food adjacent thereto in a refrigerator. Such frost is highly undesirable since it acts as an insulator for the normal extraction of heat from the food compartments to the cooling unit thereby reducing the efiiciency thereof. Accordingly, it is desirable to remove the frost quickly without melting the food, ice cubes, etc. Hence it has been common practice to provide additional means to intermittently apply heat to the evaporator and adjacent parts to periodically remove such frost rapidly and automatically. Such defrosting means usually comprise a separate electric heater element adjacent the evaporator coil or a solenoid-operated valve which acts to pass the compressed refrigerant (such as Freon) directly from the compressor to the evaporator while bypassing the condenser and capillary tube of the refrigerant circuit. The present invention is broadly concerned with the means to control the ice thickness or the formation and melting of ice on the evaporator of any of the refrigeration systems above referred to. The present invention is more specifically concerned by way of example with control means for initiating and terminating the intermittent action of the defrosting means of a refrigeration system.

The presently known defroster control devices provide manual or automatic means to initiate the defrosting action. The manual means usually comprises a push button so that initiation depends upon human decision. The presently used automatic initiating means frequently comprise a clock mechanism to start the defrosting action after a definite time interval, such as twenty-four hours, or after a predetermined total running time of the compressor, such as twelve hours, for example. All present defroster control devices provide automatic means to control the duration (or termination) of the defrosting action. Such terminating means usually comprises a gas-filled bellows-type thermostat to shut off the defroster action when the temperature in the controlled foo-d compartment rises to a predetermined value. However, sometimes clock mechanisms are also used to control duration.

A novel means for terminating the defrosting action which senses ice formation is disclosed in the above referred to application, and the present invention relates to improvements in the invention therein claimed.

Defroster control devices in recent years have become widely used in domestic refrigerators having a food freezer section that is separate from the so-called refrigerator or fresh food section. The freezer section in such refrigerators is provided with a fan to circulate air over the evaporator coil and the frozen food products. With this construction and with intermittent defrosting of the freezer evaporator, frost never forms on the food; and the melted frost from the evaporator coil is disposed of automatically.

It has always been important to terminate the defrosting action as soon as all of the frost melts in order to prevent unnecessary heating of the food compartments and possible melting of frozen foods therein. However the initiation of the defrosting action has not been too critical in refrigerators that lower the temperature only slightly below freezing, such as to 25-28 F., as in the fresh food compartment. But when defrosting the freezer sections of refrigerators having two food compartments, control of initiation with temperature-sensing termination is somewhat more critical. This requirement is valid since near-zero degree temperatures are maintained in the freezer section to promote rapid freezing of foods placed therein, and to assure that the desired freezing is not hampered by insulation produced by excessive formation of frost. This problem is even more severe because of the loss in efficiency caused by transferring heat twice; the heat first is transferred from the food to the circulating air, and secondly from this air to the evaporator which must maintain a temperature of about minus 20 F.

The termination or duration of a defrosting cycle, if correct, should not be a function of time alone. Much worse, clock mechanisms not only are complex and costly but are very unreliable and are likely to become so noisy as to require replacement.

For termination of the defrosting cycle, gas filled bellows which sense only compartment temperature are not only costly, but the gas therein is adversely affected by variations in air density. Accordingly, altitude or air density compensation means frequently are provided to compensate for the low atmospheric pressures such as normally exist at Denver, Colorado, for example. Also, the terminating temperature of bimetal snap elements usually varies plus or minus 5 F in production units.

It should be appreciated, of course, that the melting of frost or frozen food is not only a function of temperature of the surrounding materials but a function of time as well. Frozen foods or frost will melt in a short time at high ambient temperature, but can withstand ambient temperatures of a few degrees above freezing for a relatively long time without deterioration. It has been found that present defroster controls which sense only temperature act to turn off the frost-destroying heating element too soon if the frost formation is heavy and if the calibration has been established on the basis of a light frost accumulation.

In those applications in which any controlled material is fragile or pliable, such as frost, the past attempts to mechanically sense the thickness of such pliable material (frost for example) have required that the sensing member apply a force against the material which tends to crush 3 or deform the surface thereof; this action, in turn, tends to produce inaccurate or inconsistent results.

Secondly, in some of the past attempts to mechanically sense the thickness or amount of material forming on a base, as above discussed, the control means (which usually includes means such as an electric switch) is moved gradually as a function of the formation of the material. In this instance, the operation of the electric switch is critical since its snap action must be set carefully to correspond exactly to the correct thickness of accumulated material.

A broad object of the present invention is to provide a simple and novel mechanism to control the amount or thickness of formation of any substantially firm or solid material on any solid base.

Another broad object of the present invention is to provide a mechanism to control the amount or thickness of formation of any material as described in the preceding paragraph, in which a periodically movable member is provided to sense the material accumulation with a force that will not deform the material to produce erratic measurement thereof, and having particular utility when the material forms slowly.

A further broad object of the present invention is to provide a mechanism to control the amount or thickness of formation of any material, as described in either of the preceding two paragraphs, in which the control means is operated only after the material forms to substantially the desired predetermined amount or thickness.

A primary object of the present invention is to provide in an automatic defroster control device simple, inexpensive, quiet, trouble-free and consistent means to effect initiation of a defrosting system as by a direct measurement of the thickness of the frost formation.

Another object of the present invention is to provide in a control device of the type defined above in which novel, reliable, and simple mechanical control mechanism is incorporated to accomplish the desired result, which novel mechanism may be used, per se, in refrigerator or other control devices associated with any controlled condition other than the formation of frost.

Another object of the present invention is to provide an automatic defroster control for a refrigerator having mechanically operated means to initiate the defrosting action as a direct function of the thickness of frost formation, and having means to terminate the defrosting action which is dependent directly on the melting of the frost.

A further object of the present invention is to provide in an automatic defroster control system novel means to control the duration (and termination) of the defrosting action including a sensing member wholly or partial-1y immersed in a vessel in the flow path of melted frost and including means to initiate the defrosting action when first starting the refrigerator after installation and before the ice-containing vessel is filled with water.

Other objects and advantages of the invention will become apparent from the following description and from the accompanying drawings, in which:

FIG. 1 is a somewhat diagrammatic illustration-of a refrigerator having a freezer section with the device of the present invention shown in its operative relation to the several components of the refrigerator;

FIG. 2 is an elevational view of a device (with its cover removed) for controlling the duration of the defrosting action and for terminating same;

FIG. 3 shows a somewhat diagrammatic partial sectional view of One form of the control device of the present invention in which the means for initiating the defrosting action is actuated as a result of normal cycling of the compressor;

FIG. 4 is a sectional view along the line 4-4 of FIG. 3 showing one form of ice-sensing means for terminating the defroster action;

FIG. 5 is a fragmentary side view of the element shown in FIG- 3 which senses the formation of ice;

- FIG. 6 is a fragmentary side view of another form of sensing means operated by direct measurement of the elimination or reduction of ice from the evaporator unlt; and

FIG. 7 is a fragmentary side view of another form of 1 termination sensing means combining the features of the forms shown in FIGS. 3 and 6.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phaseology or terminology employed herein is for the purpose of description and not of limitation.

In a broader aspect of the inventive concept, I provide a controldevice to effect a change in condition, such as bulk or thickness, of any firm or solid material such as frost for example. I provide control means for regulating the change, such as a switch in an electric circuit, and actuating means preferably movable independent of the control means and disposed to operate same periodically. I provide sensing means mounted at a predetermined relationship with respect to the material and movable in relation thereto intermittently in response to the periodic movements of the actuating means. The sensing means is disposed to prevent the actuating means from operating the control means whenever the intermittent movements of the sensing means is not blocked or prevented by the bulk or mass of the material; but whenever the intermittent movements of the sensing means is blocked or prevented by the bulk of the material, the actuating means can then operate the control means.

In addition, the foregoing combination may be arranged for those applications in which the material is pliable or fragile (such as frost), to provide that the force of the movable sensing element acting on the pliable material is independent of and substantially less than the force of the actuating means for operating the control means; so that the force of the sensing means does not crush or deform the material to cause inaccurate or inconsistent results.

In accordance with the specific form of the invention shown herein, I provide an automatic ice-thickness control for a refrigeration machine in which the detrimental factors of present controls such as high cost, complexity, excessive noise, unreliability, inconsistency, and variations with air density are eliminated, and which will initiate the melting of ice or frost from the evaporator (or other ice forming surface) after a predetermined thickness of ice or frost is formed; and after the ice or frost is melted as desired,the control will terminate the melting action. I provide such desirable initiating action by a mechanical construction in which an actuating member is intermittently power-operated and is disposed for occasional engagement and activation of the terminatmg means. A sensing element is provided to move toward the cooling unit in response to each of the initial movements of the power-operated member when insufficient ice exists on the evaporator. The sensing element includes means upon such intermittent movements thereof to prevent the power-operated member from engaging and activating the terminating means when insufficient frost or ice has formed on the cooling unit, but to enable engagement with and activation of the terminating means Whenever the ice or frost has formed to a predetermined thickness to block the movement of the sensing element. The power means, in the form shown, comprises a solenoid which is operated upon each normal cycle of the compressor, as by the starting switch for the compressor motor. The power means may comprise any of the conventional power sources frequently used for defroster controls, such as the refrigerator door, for example. Although any means for controlling the duration of the defrosting cycle may be used and operated by the,

above-described initiating means, I prefer to use a novel means either dependent on the melting of ice or other freezable liquid in a vessel located in the flow path of melting frost (if water is the liquid in the vessel) to control this duration or by direct measurement of the melting of the ice or frost, or by a combination thereof. Both forms of such novel means to terminate the defrost cycle have special utility when used in combination with my novel cycle initiating means.

Since frost is fragile and pliable, only a very light force can be applied thereon to sense its thickness with acceptable consistency and accuracy. As above discussed, the force and travel of the sensing element in my invention can he very small compared to the force and travel of the actuating member; and this small sensing force and travel controls the larger separate force and travel. Thus the action is similar to any fluid or electric servomechanism in which a signal at a small energy level is amplified and accurately reproduced at a much higher energy level by a separate and greater source of energy.

Referring now to the drawings, and particularly FIG. 1, there is shown diagrammatically by way of example an installation of the present invention as a defroster control unit in operative relation to a refrigeration machine and the electric circuits necessary for operation of the control unit. The entire defroster control may be considered to comprise two components. A control unit which controls the duration (or termination) of the defrosting action, as shown detailed in FIG. 2, is the first component; and the initiating mechanism or means 17 is the second component. In FIG. 1, a typical refrigerator is illustrated having a cabinet (in dotted outline) formin a food freezer section 19 and a fresh food section 21 divided by Walls 23 and 25. The refrigerant system includes the usual compressor C which sends the refrigerant through a tube 27 to a condenser D, thence through a capillary tube 29, to be expanded through a frozen food evaporator or cooling unit 30 of the usual tube coil construction, where it either returns under vacuum to the compressor through tube 31 or flows to a second evaporator 30a (shown dotted) for the fresh food section 21, all in a manner well known to those skilled in the art. A conventional solenoid-controlled valve S is mounted in a tube 32 which may by-pass refrigerant around the condenser directly from the compressor to the evaporator coil 30. When the solenoid valve is opened, by action of the defroster control to be described, the hot refrigerant passes directly from the compressor through the evaporator which quickly melts all the frost formed thereon. The melted frost drops into a trough 34 mounted at the back of the freezer section where the water flows through a tube 36 to a pan 38, where the heat of the condenser helps the melted frost to evaporate. In normal operation, the contents of the freezer'section are cooled by air circulated by a small air fan (not shown) which causes air to circulate around the freezer section and over the evaporator 30.

The electric motor for the compressor includes the conventional starting winding B and running winding R with the usual starting switch 37 for cutting out the starting winding after a short operation of the motor following each closure of thermostat switch 58.

Temporarily referring to FIG. 2, to be discussed in detail hereinafter, the control unit 15 includes control means comprising an electric switch having a fixed contact 39 connected to a terminal 4t and an opposed fixed contact 42 connected to a terminal 44. A movable contact 46 is carried by an arm 48 swingable about a knife edge connection with a support 50 and is connected to a stationary terminal 52. A strong extension spring 53 is connected at one end to the contact arm 48 and at its other end to an arm 54. The switch is shown in its normal position without the defrosting system in operation, and in this position terminal 52 is electrically connected to terminal 40 through contact 46 resting on contact 39 by the force of spring 53. When arm 54 is moved to the dotted position 54' by means to be described, spring 53 is moved over center to the right, as viewed in FIG. 2, so that contact 46 snaps against contact 42 to electrically disconnect terminal 52 from terminal 40 and connect to terminal 44. In this position, however, the spring 53 maintains a relatively large force urging the arm 54 back to the full line position shown in the drawings since the position of the spring is always at the left of the fulcrum of the arm 54. When arm 54 is moved back to its original position shown, the contact 46 is snapped back to its original position shown in FIG. 2.

Again referring to FIG. 1, line voltage of power line L is directed through a wire 56 to a two pole thermostat switch 58 for the freezer section which energizes compressor.C when the temperature at a bulb 60 rises to a predetermined value. Line voltage from wire 56 also is taken to terminal 52 of the defroster control unit 15. Another conductor 62 may optionally be included to connect the normally closed pole of switch 58 to terminal 44 (FIG. 2). Also the solenoid valve S is connected to terminal 44 by wire 64 in parallel with the compressor when the circuit to the latter is closed only through the switch in unit 15.

The action of the refrigerator and defroster control is as follows. When thermostat switch 53 closes the left pole as viewed in FIG. 1, with the switch of unit 15 in the position shown in FIG. 2, the compressor lowers the freezer temperature in a normal manner until shut off by the thermostat. However, when the defroster control causes arm 54 to move to position 54 in a manner to be described, the compressor C would be operated regardless of the position of switch 58, and solenoid valve S opens the by-pass line 32 to pass hot gas through the evaporator 30 until all the frost melts and is collected in pan 38 as described. After all the frost is melted, the defroster control causes arm 54 and contact 46 to return to the position shown in FIG. 2, by means to be described.

It should be appreciated that there are many possible combinations of refrigerator arrangements and circuits. For example, a refrigerator may have one or two separately closed compartments; in a two compartment unit, the freezer section may be on top or below; or the defrosting system may utilize hot gas or electrical resistance units, etc. Also, the defroster control 15, 17 might be mounted in many different portions of the refrigerator, such as at the back of the freezer section between the inner or outer liner, or mounted inside the freezer compartment directly on the coil 30. In addition, the icethickness control device can be used for any kind of refrigerating or other machine, not just as a defroster control for the freezer section of a domestic refrigerator as described in connection with the principal form of the invention. Hence, the particular combination shown in FIG. 1 is merely illustrative, in which a defroster control is shown mounted between the inner liners 23 and 25 which separate compartments 19 and 21, for controlling the frost in the freezer section 19 shown in the lower portion of a two compartment domestic refrigerator.

Now referring to FIGS. 2-4, the means to control the duration (hence the termination) of the defrosting section will be now explained. In unit 15, the mechanism illustrated herein is encased in a housing 68 of any suitable material such as sheet metal with three sides 68a folded up from the base. A fourth side is formed by the electrical insulating base 69 for the switch, which base has a plurality of projections 69a for insertion into holes in the sheet metal housing and cover to be secured together by upsetting portions of the sheet metal. The housing 68,

includes projections or tabs 68b cooperating with suitable openings in a cover '70 (FIG. 3) to be staked or bent to secure the cover to the housing. In unit 15, arm 54- carries a detent member 72 hinged thereto at one end to permit angular movements of the detent in relation to arm 54. A light extension spring '74 is suitably secured at frozen in normal refrigerator operation.

one end to arm 54 and at its other end to detent 7 2 urging the detent downwardly into engagement with a cam or guide member 76 which is secured to one side of housing 68 by suitable means as by staking or soldering.

A bushing member 78 includes a hexagonal flange which is secured to the inside of housing 68 by suitable means as by soldering or staking. The bushing 78 includes a bore to journal a shaft 80 which carries a latch member 82 secured thereto for angular movements with the shaft. A very light extension spring 84 is suitably secured at one end to housing 68 and at its other end to a portion 82b of latch member 82 to urge same in a-counterclockwise direction into the free position shown in FIG. 2. Detent 72 includes a catch portion 86 disposed to engage a latch arm 82a of latch member 82 in a manner to be described. A rectangular shaft 90 is supported and guided by a tab 92 (struck inwardly from housing 68) for axial sliding movements to abut and actuate arm 54 as shown.

In FIG. 3, unit is shown with its cover 70 installed and the unit mounted in its operative position between inner walls 23 and 25 of chambers 19 and 21, respectively. Shaft 80 projects outwardly through cover 70 (perpendicular to the drawing) and has a sensing arm 94 secured thereto by suitable means, as by a set screw, for angular movements therewith. A small vessel 96, as shown in FIGS. 3 and 4, is suitably secured to a portion of the evaporator tubing such that the vessel is below the tubing. The vessel may be made of any suitable material, but a metal such as aluminum is desirable to provide the highest heat conductivity which is facilitated by wrapping a portion 96a of the vessel around the tube. The vessel is mounted so that an offset sensing portion 94a of arm 94 is suspended inside an ice chamber 98 formed by the vessel. A light leaf spring member 100 may be secured to arm 94, as by rivets, when water is used in the vessel and is slightly prebent to ride against the surface of portion 96a in operative movements of arm 94 for reasons to be discussed.

The operation of the defrosting duration or termination control unit above-described is as follows. Referring to FIGS. 1-4, assume that chamber 98of vessel 96 in completely filled with water or other freezable liquid which is After frost forms on the evaporator to a predetermined thickness, shaft 90 is automatically moved temporarily to the left by means to be described until arm 54 is moved to the position at 54'. This action causes contact 46 to move against contact 42 which operates the compressor and solenoid valve to send hot gas through evaporator 30 for melting and disposing of the frost in a manner previously described. At this time the iceor frozen liquid in vessel 96 is also subjected to heat somewhat by radiation but primarily by conduction from the tube 30, which is the reason why a vessel made of a metal of high heat conductivity is desirable. Also, movement of the switch arm to the position at 54' carries detent 72 leftward until spring 74 causes catch portion 86 to engage latch arm 82a. The force on shaft 90 is soon removed, as will be described. Then the force of spring 53 tends to return arm 54 into the position shown with a force that easily overpowers the force of spring 84. Such forces are transmitted through detent 72- which now abuts latch arm 82a tending to impart angular movement to latch member 82. However, such angular movements are prevented by arm 94 now embedded within the ice or frozen liquid in vessel 96 which tends to be compressed between the left edge of the sensing portion 94a and the left inside wall 96b of the vessel as viewed in FIG. 3. Thus, the ice acts as an ice (or frozen liquid) link which grows smaller gradually as the ice or frozen liquid progressively melts since contact with the melting ice is maintained by spring 53. As arm 54 with its detent member 72 gradually moves rightwardly when the ice in vessel 96 slowly'melts,

a cam portion 72a of the detent member contacts cam 76 which gradually raises the detent member in opposition to spring 74. After a predetermined travel of arm 54 and detent 72 which is calibrated to occur when all the frost is melted, the catch portion 86 disengages from latch arm 82a. This instantly causes two simultaneous actions as follows: The first action is that spring 84 instantly returns latch member 82 into the angular position shown in FIG. 2 in which arm 82b contacts the lower side of the housing; accordingly the sensing portion 94a is moved rightwardly (FIG. 3) through the path of melted ice (water) and restored to the position shown. The second simultaneous action is that spring 53 causes arm 54 and detent 72 to snap into the position shown in FIG. 2, which also moves the contact 46 into the position shown against contact 39. This terminating action causes the solenoid valve S to shut off the flow of hot gas through the by-pass tube 32 so that refrigerator operation is again normal. The compressor is again controlled only by thermostat 58, and the ice in the vessel 96 soon freezes so that the defrosting cycle can be repeated as above described after a predetermined thickness of frost is formed.

It is important to appreciate that all the ice in vessel 96 may not melt, but only that portion adjacent the metal surfaces such as at sensor portion 94a and the interior walls of vessel 96. The unit 15 is so calibrated that when all the frost on the evaporator is melted, the detent member 72 is disengaged from latch arm 82a after a predetermined travel. This can be controlled by numerous variables such as the height of chamber 98, the thickness of sensing portion 94a, the heat conductivity of the material used for the sensing portion and vessel, the vertical adjustment position of cam 76, etc. It is also important to appreciate that the detent travel is always larger than (and easily includes) the travel necessary to cause contact point 46 to snap between contacts 39 and 42. Hence, the production setting of the switch snap is not in the least critical, as in many prior devices; because for production units it is only necessary to provide the relatively large travel of detent 72, such as by setting the vertical position of release cam 76.

When the refrigerator is first placed in service and water is to be the liquid in the vessel, the present invention provides a novel means which may be employed so that it is unnecessary to fill chamber 98 with water initially to make the defrosting system operative. The construction also produces a more accurate calibration since the device is arranged to sense the accumulation of frost directly. As explained above, leaf spring 100 contacts either tube 30 or vessel portion 96a in all positions of arm 94. Also, vessel 96 is mounted below tube 30 to be in the flow path of melting frost to keep chamber 98 completely filled, whereas the overflow falls into trough 34 to be evaporated as described. As explained above, the control is calibrated to terminate the defrosting action after a predetermined melting time dependent on numerous factors including a completely full amount of water in vessel 96. Thus, as calibrated, if chamber 98 is only one-half full, the defrosting action would terminate before all the frost is melted.

If the leaf spring 100 is employed, the defrosting action is developed, as follows, starting with a completely empty vessel at the time the refrigerator is first placed in service. When the frost forms to its predetermined thickness on tube 30 (FIG. 4), a portion of the frost covers leaf spring 100. Then when the frost forms to its predetermined thickness and shaft is moved to start the first defrost heating action, arm 94 is moved gradually to the left by spring 53 as the frost covering leaf spring melts until detent 72 disengages from latch arm 82a. The frost tends to be compressed between the leaf spring 100 and a stop tab or abutment 96c (FIG. 3) which projects transverse to the tube. However, without water in the vessel (as calibrated), only a small portion of the frost melts on this first cycle but some of this melted frost falls into chamber 96 to cover perhaps only the end of sensor portion 94a. Then the second defroster cycle will be longer due to the small amount of ice added in vessel 96, so that a larger percentage of the frost is melted during this second cycle. Some of the additional melted frost again falls in chamber 98, so that a higher percentage of frost is melted on each subsequent defrosting cycle. This action continues until the vessel 96 is completely full so that all the frost is melted during each subsequent cycle as calibrated. In actual operation, the vessel is full after only the first few cycles when the refrigerator is first placed in service. The leaf spring 100 might be omitted if arm 94 were mounted close enough to be embedded in the frost that forms on tube 30. However, to accommodate production variations, the leaf spring 100 (or equivalent) may be provided. In any case, the calibration is partly produced by the arm 94 or leaf spring 100 compressing frost between it and abutment 96c and partly by the sensing portion 94a compressing ice between it and thewall 96b of the collecting vessel.

The principle of the duration control unit 15 as above described, except for the automatic vessel-filling means shown in FIG. 4, is disclosed in my Patent No. 2,949,016, in which the theoretical concepts are discussed in more detail. It is important to appreciate that any duration (termination) control means may be used or operated by the novel initiating control means now to be described. However, the inherent simplicity, reliability, consistency, function accuracy and potentially low cost of the duration control disclosed herein, particularly with improvements to be discussed in relation to FIGS. 6 and 7, provides an inventive combination with the iniitating means now to be described.

Now consider the means 17 to initiate operation of the duration control device, which in the specific duration device disclosed herein, comprises the means to effect periodic or intermittent movement of shaft 90 after a predetermined amount of frost has formed. Referring to FIGS. 3 and 5, shaft 90 is disposed to be actuated occasionally by a second shaft or pin 104, or the like, carried by an armature 106 of a solenoid 108 secured in a housing 110, which is connected to or integral with the housing 68 of the terminating means 15. Means are provided to detect or sense by direct measurement the formation of frost on tube 30. In the form shown, such means comprise asensing member 116, made of any suitable material such as metal strip, which is supported by a pair of parallel leaf springs 118 and 120 to provide frictionless movements in a direction transverse to the direction of movement of the armature and shaft 90. One end of each leaf spring is secured to a fixed part of the control unit, such as to the housing of the solenoid 108, as shown. The other end of each leaf spring is secured to the sensing member 116, as by rivets, to provide free floating movement thereof which is entirely frictionless. The leaf springs, which may be made of any suitable material such as Phosphor bronze, stainless steel, etc., are pre-bent in a downward direction so that when the sensing member is in the position shown, it 1s subjected to a downward spring force. Such prebendmg of the leaf springs provides a light force which enables the control to be mounted in positions other than vertical. The sensing member is, as illustrated in FIG. 3, positioned between the ends of shaft 90 and pin 104 to completely clear these elements in its transverse movements.

A cam member 122 is secured to but offset from pin 104 by suitable means, as by a rivet, to be carried therewith during movements of the armature 106. The cam portion of member 122 cooperates with an arm or extension 116a (FIG. 5) of sensing member 116 to maintain this member in its desired positions. A spring 124 acts on the end of cam member .122 to act oppositely to the electromotive force of armature 106, and the cam member abuts the solenoid as shown when it is de-energized, thereby to position the armature and its pin. The cam portion of member 122 is made at any suitable angle, such as 45 for example; then when the solenoid 108 is energized, the leftward movement of armature 106 allows the sensing member 1116 to move downwardly toward the evaporator tube 30 under the influence of the initial (pre-bent) force of leaf springs 118 and 120 and/ or by gravity. When solenoid 108 is de-energized, spring 124 is sufficiently strong to overpower the force of leaf springs 118 and 120 and return the cam and armature to their original positions, which also lifts the sensing member to the position shown in FIG. 3.

The portion of the sensing member between the leaf springs V118 and .120 has a suitable aperture 126 or its equivalent which, in the position shown, aligns with and is slightly larger than pin 104. The aperture might comprise an elongated hole, or merely a surface-edge, which can be moved into and out of the path of pin 104. The sensing mern'ber also includes a sensor tab or portion 116a which, in the position shown, is maintained at a predetermined distance T from the evaporator coil 30. The left end of pin 104 is positioned initially at a predetermined distance from the hole 126 of sensing member 116, such as inch for example, so that the pin (and armature) must travel this distance before passing into (and through) the hole 126, only during conditions to be discussed.

The solenoid is connected in parallel with the refrigerator motor starter winding B by wires 128 and 130, as shown in FIG. 1. In this circuit, each time the thermostat switch 58 closes, the solenoid 108 is energized to urge armature 106 and its pin 104 to the left, until the usual starter switch 37 opens a few seconds later to cut out the winding B. At this time, the spring 124 returns the armature and pin to the position shown, and would not be en ergized again until switch 58 again closes at the next compressor cycle. The solenoid 108 is thus pulsed at each actuation of the refrigerator motor. The solenoid also could be pulsed by any other intermittently operated switch normally included in refrigerators (instead of by switch 58) such, for example, as by the door-light switch.

Now the complete operation of the initiating mechanism 17 can be explained. When the switch 58 is closed wit-h little or no frost on tube 30 as above described, the sensing member 1 16 moves downward in response to and simultaneously with the leftward movement of armature 106 and pin 104. However, as previously discussed, the pin 104 must travel a certain distance, as & inch, before reaching hole 126 which hole at that instant has been displaced downwardly out of alignment with the pin. Thus, with insuficient frost on tube 30, the pin 104 strikes a solid portion of the sensing member 116 and is thereby prevented from contacting shaft by the restraint of leaf springs 118 and 120. However, after the frost builds up on tube 30 to a thickness T, the sensing member is blocked by the frost for downward movement. Then, the next closure of switch 58 causes solenoid 108 to move pin 104 which then passes through the hole 126 to actuate shaft 90, which in turn activates the duration control or terminating means 15 as above described. Meanwhile, the solenoid 108 is de-energized when the starter switch 37 opens a few seconds after the compressor motor starts, so that spring 124 returns all elements of the unit 17 to their positions shown in FIG. 1. Then, after all the frost melts and the defrosting cycle is terminated, the entire defroster control is ready for the next cycle.

Thus, at each compressor cycle, solenoid 108 is energized for only a few seconds by the starting switch 37. If insufiicient frost exists on tube 30, pin 104 is blocked from actuating the terminating means 15 by downward movement of the sensing member in response to the camaction caused by the initial movement of the armature. When frost forms to a predetermined thickness, this downward movement of the sensing member is prevented 1 1 by the frost so that pin 104 is then able to pass through the aperture .126 for activating the duration control 15. Hence, the defrosting action is started at the first compressor cycle following the build up of frost to a predetermined thickness T. In the interim, the sensing memher is caused to move occasionally toward the tube 30 to feel or sense the frost upon each intermittent com-. pressor cycle until the frost builds up to the thickness T.

It is obvious from the foregoing that several reversals in elements could be made without departing in any way from the spirit of the invention. For example the elements could be arranged to have the leaf springs 118 and 120 with their supported sensing member all carried by either pin 104 or shaft 90. However, with either of these reversals, the sensor tab 1160 would slide along the frost with movements of pin 104 or shaft 90, so that the form shown herein is believed preferable. Also, it is apparent that the leaf springs 118 and 120 could be eliminated;'and any mechanical guide means could be provided to constrain the sensing member .116 to its vertical sensing movements without departing from the scope of the invention; but with this equivalent construction the pre-bending force of the leaf springs would be replaced by any other biasing force, such as by a coil spring. However, since the forces involved must be very light to provide the desired servo action above referred to, it is highly important to reduce friction to a minimum. Accordingly, the leaf spring supports are desirable since they not only provide frictionless movement of the sensing member 116, but constrain the member to a fixed path without play, which would prevail with a sliding type of guide means. It is also obvious that it is not essential for the pin 104 itself to strike shaft 90 after passing through or by the aperture 126. For example, any means or member movable with armature 106 can contact shaft 90 and can be mounted on either side of the Sensing member 116 to effect operation of the control means when shaft 104 passes through or by aperture 126.

Referring to FIG. 1, if an electric heater is provided to melt the frost instead of the hot-gas by-pass tube 32 and valve S, the wire 102 would then be connected to terminal 40 (FIG. 2). With this arrangement, the compressor would be turned Off when the defroster cycle starts. Also, with the hot-gas system shown in FIG. 1 by way of example, wire 62 might be deleted if desired since the compressor would continue to run during the defrost cycle in attempting to lower the temperature at bulb 60.

It is apparent that the solenoid power unit can pro vide excellent trouble-free and noise-free service since it operates only a few seconds at each compressor cycle. However, if desired, any other of the usual power means, such as clocks, door power, etc., may be employed without departing from the scope of the invention.

FIG. 6 shows a modified form of the control device of FIGS. 2 and 3 in which the termination control unit includes a sensing means which depends directly on the thickness of ice or frost on the evaporator tube 30. With the ice vessel type of sensor of FIGS. 3 and 4, the sensor moves through the ice and is calibrated as a function of themelting of ice to terminate the defrost cycle when all the frost is melted. In FIG. 6, an ice sensor 132 includes a wide flange 132a which may have a rough surface and is set (when the defroster control is inactive) at the same predetermined distance T from the tube 30 as for tab 1160. A right angle bend is provided in tube 30 to cooperate with the sensor 132 which is supported by shaft 80 extended sufficiently to enable the sensor tab 1160 to also be positioned at the same distance T from tube 30 as tab 132a, for operating the mechanism 17 as above described.

In operation, after the ice or frost 134 builds up to a thickness T and mechanism 17 activates the unit 15 as above described, the spring 53 (FIG. 2) causes the sensor 132 to abut abainst and follow the ice as it gradually melts. When all the ice is melted and the flange 132a reaches tube 30, the detent 72 is set to release from latch arm 82a (FIG. 2) so that spring 84 instantly returns the sensor 132 to its free position as shown in FIG. 6. While the form shown in FIG. 6 would be less costly and functions directly in response to changes in the thickness of ice 134, the control device would be mounted at or near the last portion of the frost to melt. However, in the form shown in FIGS. 3 and 4, the control device can be mounted anywhere on the evaporator 30, since th travel of the sensing arm 94 can be calibrated to terminate when the last portion of frost melts anywhere on the evaporator. I have found the form of sensing means shown in FIGS. 3 and 4 to be very accurate and consistent.

The form of sensing means shown in FIG. 6 is particularly desirable for conventional ice-bank commercial refrigeration systems. In this type of refrigeration system, a large body of water surrounds a relatively small evaporator unit. During light-load periods, the compressor operates to build up a body of ice to a predetermined thickness surrounding the evaporator; and during heavy loads this body of ice provides the refrigeration. The control device of FIG. 6 operates to turn off the compressor when the ice builds up to the desired thickness, and starts the compressor when the ice thickness diminishes to any desired amount determined by sensor-flange 132a moving with the melted ice 134 in cooperation with cam 76 (FIG. 2). For this adaptation of my ice-control invention, wires 102 and 64 (FIG. 1) would not be required, and wire 62 would be connected to terminal 40 (FIG. 2), and wires 128 and 130 would be connected to any intermittently operated switch in place of switch 37, as by the conventional door-light switch or any conventional clock-operated switch. The formation of ice cubes also could be controlled by the present invention in a similar manner.

FIG. 7 shows means to sense the melting of ice which enables design selection of any combination of the features of FIGS. 3 and 6. In FIG. 7, the sensing arm 138 carries a hinged ice sensor having a curved or cylindrical flange 140a which is set at the same predetermined distance T from tube 30 as is the tab 1160. The arm 138 is of any desired length, as shown, to move sensor 140a in any angular direction. A vessel 142 is open at the top, and tube 30 passes through and is sealed to the end walls of the vessel such as the left wall 142a. One or more overflow holes 144 may be provided in any of various vertical positions as will be discussed. When the ice 134 forms on tube 30 to a thickness T and unit 15 is activated by the initiating mechanism 17, the spring 53 (FIG. 2) causes arm 138 to move sensor 140 down and to the left, as viewed in FIG. 7. .Thus, the sensor not only follows the melting of ice downward but will partially abut some of the ice between its left end and the fixed wall 142a, similar to the action in FIG. 3..

The device can be calibrated in this manner only with respect to the wall 142a, and the rest of the vessel can be deleted or a hole 144 provided at the bottom of the vessel. If the overflow hole 144 is located at half the vessel depth, for example, then the melted frost from preceding cycles would collect and freeze to this depth. This ice would act to delay the melting of frost on subsequent cycles, so that the device could be calibrated to terminate when the last portion of frost melts and when such last portion is remote from the defroster control. If the overflow hole is made still higher so that th lower extremities of the curved sensor flange 140a are embedded in the collected ice, the immersed portions of the sensor must travel through the ice, so that the calibration would approach the type of action of the form shown in FIG. 3. If the overflow hole 144 is entirely omitted, the collected ice would build up to the top level of the frost at thickness T. Hence, without the overflow hole 144, the form shown in FIG. 7 is very similar in action to the form shown in FIG. 3, except that the leaf spring element 100 is not needed in FIG. 7. With any 13 of the above-described calibrations, the arm 138 can be made short enough so that the bottom of the arc of travel of sensor flange 140a can be adjusted to almost touch the tube 30.

In summary, referring to the form of the inventlon d1sclosed in FIGS. 3, 6 and 7, numerous tests of this concept have shown that the defroster control can be calibrated satisfactorily to terminate the defrosting action without vessel 96 or vessel 142 by using only the direct frost sensor (leaf spring 100) or equivalent abutting means as a sensing member to entrap frost between the sensor and a projection such as element 96c or equivalent stop means.

However in this instance, the control device must be,

mounted on the evaporator coil 30 somewhat near the last portion of frost to melt. When the vessel 96 is combined with the abutting frost-sensor 1%, although the cost increases slightly, the control unit can be mounted anywhere on the evaporator coil since the travel of sensor arm 94 can be calibrated to terminate the defrosting action at a position corresponding to the last portion of frost to melt, even if remote from the control device.

Having now described my invention, it is important to appreciate that the defrosting control system disclosed herein for domestic refrigerators may be applied equally well to control the ice-thickness in any refrigeration, airconditioning, heat pumps, soft drink coolers, or any other mechanism requiring the control of the formation and/ or melting of ice.

In its broadest aspect, the control device of the present invention can be used in any application in which any substantially firm or solid material is subject-ed to a change in condition such as in its size, height, depth, thickness, etc., of its bulk or mass, and in which device means are provided to sense such change in condition (or to detect the presence or absence of such mass or body) to control the bulk of said material to any predetermined value. In those instances in which a mass is in one place at one time but is not present at another time, such changes can also be sensed by the control device of the present invention. Other uses and modifications of the invention may be made without departing from the spirit and scope of the appended claims.

What I claim is:

1. In a control device associated with apparatus having a surface subject to the formation of ice adjacent thereto, control means for regulating the amount of said ice, actuating means adapted to operate said control means, sensing means directly dependent on the formation of said ice and disposedto move into the path of travel of said actuating means to block same from opera-ting said control means when said ice formation is less than a predetermined amount, said sensing means including means disposed to abut said ice for preventing said blocking movements of said sensing means to enable said actuating means to be operatively connected mechanically to said control means for operation thereof after the said ice has formed to substantially said predetermined amount for blocking said movements of said sensing means.

2. In a control device associated with apparatus having a surface subject to the formation of ice adjacent thereto, the combination of; control means for regulating the amount of said ice, actuating means including a movable member normally completely disconnected from said control means but adapted to directly operate said control means, sensing means dependent on the formation of said ice and including a sensing element movable in response to movements of said actuating member into the path of travel of said actuating means to block same from operating said controlmeans at least in one position of said element when said ice formation is less than a predetermined amount, said sensing element at a second position thereof including means for preventing said blocking movement of said sensing means to enable said actuating member to be operatively connected mechanically to said control means for operation thereof after the said ice has formed to substantially said predetermined amount for blocking said movements of said element.

3. In a control device for a refrigeration system having a cooling unit subject to the formation of ice adjacent thereto, said refrigeration system including a source of energy normally supplied to said system, the combination of; control means for effecting a change in the state of at least a portion of said ice, actuating means powered by said source of energy and adapted to occasionally operate said control means automatically during all conditions of operation of said system and including an intermittently movable element providing a force for said occasional operation, sensing means adjacent said element and having a portion mounted at a predetermined distance from said cooling unit and movable in relation thereto in response to said intermittent movements of said element when the amount of ice on said cooling unit is sufficiently less than said corresponding predetermined distance to enable said relative movements, means providing a force separate and independent of said first-named force and tending to urge said portion against said ice, said sensing means including means for enabling said element to be operatively connected to said control means for operation thereof at the first said intermittent movement of said element following sufiicient formation of ice to substantially block said movement of said portion of said sensing means for effecting a change in said state of said ice, and means for terminating the action of said control means.

4. In a control device for a refrigeration system having a cooling unit subject to the formation of ice adjacent thereto, the combination of, control means for regulating the thickness of said ice, a member movable in one direction for operating said control means, force-producing means adapted to occasionally operate said control means and including an element intermittently movable in substantially said first-named one direction, sensing means having a portion mounted at a predetermined distance from said cooling unit and movable in relation thereto in a direction transverse to said first direction in response to said intermittent movements of said element when the thickness of ice on said cooling unit is sufficiently less than said corresponding predetermined distance to enable said relative movements, said sensing means including means for enabling said element to be operatively connected to said member for operation thereof at the first said intermittent movement of said element following sufficient formation of ice to substantially block said movement of said sensing means for effecting a change in said thickness of said ice, and means for terminating the action of said control means after the thickness of said ice has changed a predetermined amount.

5. In a control device for a refrigeration system having a cooling unit subject to the formation of ice adjacent thereto, the combination of, control means for effecting a change in the state of at least a portion of said ice, actuating means adapted to occasionally operate said control means and including an intermittently movable element, sensing means having a portion mounted at a predetermined distance from said cooling unit and movable in relation thereto in response to said intermittent movements of said element when the amount of ice on said cooling unit is sufficiently less than said corresponding predetermined distance to enable said relative movements, said sensing means including means for enabling said element to effect operation of said control means at the first said intermittent movement of said element following sufficient formation of ice to substantially block said movement of said sensing means for effecting a change in said state of said ice, means for terminating the action of said control means after the state of said ice has changed a predetermined amount, and frictionless swingable means imparting rigidity in one direction and acting to support said sensing means for frictionless movements in a direction transverse to said first-named one direction by mainrection in response to said intermittent movements of said element when the thickness of ice on said cooling unit is sufficiently less than said corresponding predetermined distance to enable said relative movements, said sensing means including means for enabling said element to effect operation of said control means at the first said intermittent movement of said element following sufficient formation of ice to substantially block said movement of said sensing means for effecting a change in said thickness of said ice, means for terminating the action of said control means after the thickness of said ice has changed a predetermined amount, and a frictionless pair of spaced substantially parallel leaf spring members imparting rigidity in said first-named one direction and acting to support said sensing means for said relative movements in said transverse direction without friction by maintaining said sensing means suspended completely free of sliding surface contact during said transverse movements thereof.

7. In a control device for a refrigeration system having a cooling unit subject to the formation of ice adjacent thereto, the combination of, control means for regulating the thickness of said ice, a member movable in one direction for operating said control means, force-producing means adapted to occasionally operate said control means and including an element intermittently movable in substantially said first-named one direction, sensing means having a portion mounted at a predetermined distance from said cooling unit and movable in relation thereto in a direction transverse to said first direction in response to said intermittent movements of said element when the thickness of ice on said cooling unit is sufficiently less than said corresponding predetermined distance to enable said relative movements, said sensing means including means to block said element from actuating said member upon said corresponding transverse movement of said sensing means, said sensing means also including aperture means for enabling said element to pass thereby for actuating said member at the first said intermittent movement of said element following sufficient formation of ice to substantially block said movement of said sensing means for effecting a change in said thickness of said ice, and means for terminating the action of said control means after the thickness of said ice has changed a predetermined amount.

8. In a control device for apparatus having a surface subject to the formation of ice adjacent thereto, the combination of; control means for regulating the thickness of said ice, a sensing member having a portion positioned at a predetermined distance from said surface and normally disconnected from said control means, means to actuate said control means and to operatively connect said control means to said sensing member for initiating a melting action of said ice, and means to cause said then-connected sensing member to abut against said ice and gradually move therewith as said ice progressively melts.

9. In a control device for apparatus having a surface subject to the formation of ice adjacent thereto, the combination of; control means for regulating the thickness of said ice, a sensing member having a portion positioned at a predetermined distance from said surface and normally disconnected from said control means, means to actuate said control means and to operatively connect said con- .trol means to said sensing member for initiating a melting action of said ice, force-producing means to cause said then-connected sensing member to abut against said ice and gradually move therewith in a direction toward said surface as said ice progressively melts, and means to effeet a disengagement of said connection after said ice has melted a predetermined amount for terminating said ice-melting action.

10. In a control device for a refrigeration system having a cooling unit subject to the formation of frost thereon, the combination of; control means for regulating the thickness of said frost, a sensing member having a portion positioned at a predetermined distance from a surface of said cooling unit and normally disconnected from said control means, means to actuate said control means and to connect said control means to said sensing member for initiating a melting action of said frost, means to cause said then-connected sensing member to abut against said frost and gradually move therewith in a direction at an angle with respect to said surface as said ice progressively melts.

11. In a control device for a refrigeration system having a cooling unit subject to the formation of frost there-,' on, the combination of; control means for regulating the thickness of said frost, a sensing member having a portion positioned at a predetermined distance from a surface of said cooling unit and normally disconnected from said control means, means to actuate said control means and to connect said control means to said sensing member for initiating a melting action of said frost, means to cause said then-connected sensing member to abut against said frost and gradually move therewith in a direction at an angle with respect to said surface as said ice progressively melts, and a vessel mounted adjacent to said cooling unit surface in the flow path of melted frost to collect water adjacent said cooling unit and said sensing member, and means to disengage said connection after said frost has melted for terminating said frost-melting action, whereby said water freezes to solid ice in said vessel, said ice thereafter affecting the terminating calibration of said sensing member.

12. In a control device for a refrigeration system having a cooling unit subject to the formation of frost thereon, the combination of; control means for regulating the thickness of said frost, a sensing member having a portion positioned at a predetermined distance from a surface of said cooling unit and normally disconnected from said control means, means to actuate said control means and to connect said control means to said sensing member for initiating a melting action of said frost, a firm wall adjacent said surface and substantially transverse thereto, means to cause said then-connected sensing member to abut against said frost and gradually move therewith in a direction at an angle with respect to said surface in a generally arcuate direction starting at an angle to said surface and approaching a parallel path with respect thereto tending to compress said ice between said sensing member and said wall as said ice gradually melts.

13. In a control device associated with apparatus subject to the formation of ice adjacent a surface therein, the combination of, control means for regulating an amount of ice forming on said surface, actuating means adapted to operate said control means, initiation sensing means dependent on the formation of said ice to preclude said actuating means from operating said control means when said ice formation is less than a predetermined amount, said sensing means including means to enable said actuating means to effect operation of said control means after the said ice has formed to substantially said predetermined amount for causing a melting of at least a portion of said ice, a termination sensing member having a portion positioned in a predetermined relationship with respect to said surface and normally disconnected from said control means, means to operatively connect said control means to said termination sensing member for initiating said melting action of said ice when said 1 7 actuating means operates said control means after said ice has formed to said predetermined amount, means to cause said then-connected sensing member to abut against some ice adjacent said surface and gradually move therewith as said ice progressively melts.

14. In a control device associated with apparatus hav ing a surface subject to the formation of ice adjacent thereto, the combination of, control means for regulating the amount of said ice, actuating means adapted to operate said control means, initiation sensing means dependent on the formation of said ice and inciuding a sensing element movable toward and away from said surface in response to movements of said actuating means to pre clude said actuating means from operating said control means at least in one position of said element when said ice formation is less than a predetermined amount, said sensing element in a second position thereof including means to enable said actuating means to effect operation of said control means after the said ice has formed to substantially said predetermined amount for causing a melting of at least a portion of said ice, a termination sensing member having a portion positioned in a predetermined relationship with response to said surface and normally disconnected from said control means, means to operatively connect said control means to said termination sensing member for initiating said melting action of said ice when said actuating means operates said control means after said ice has formed to said predetermined amount, force-producing means to cause said then-. connected termination sensing member to abut against said ice and gradually move therewith in a direction toward said surface as said ice progressively melts, and means to effect a disengagement of said connection after said ice has melted a predetermined amount for terminating said ice-melting action.

15. In a control device for a mechanism associated with a material subject to changes in the condition thereof, the combination of, control means for effecting a change in the condition of said material, sensing means including an element positioned in a predetermined relationship adjacent said material and periodically movable in one direction with respect thereto for detecting said changing condition of said material, said sensing means including means to effect a desired operation of said control means upon a sufficient change in said condition for regulating in a predetermined manner the condition of said material, and a pair of spaced substantially parallel leaf spring members imparting rigidity in a direction transverse to said one direction and acting to support said sensing element without friction during movements thereof in said one direction by maintaining said element suspended completely free of sliding surface contact during said movements thereof.

16. In a control device for a mechanism associated with a material subject to changes in the condition thereof, control means for effecting a change in the condition of said material, actuating means to operate said control means, sensing means including an element positioned in a predetermined relationship adjacent to said material and periodically movable in one direction with respect thereto in response to said movements of said actuating means at one condition of said material for detecting a change thereof, said sensing means including means for enabling said actuating means to effect operation of said control means upon a sufficient change in said condition to block said movements of said sensing means, and swingable means imparting rigidity in a direction substantially transverse to said one direction and acting to support said sensing means Without friction during said movements thereof in said one direction by maintaining said sensing means suspended completely free of sliding surface contact during said movements thereof.

17. In a control device for a refrigeration'system subject to the formation of ice adjacent a surface therein, the combination of, control means for regulating the thickness of said ice, means to eflect operation of said control means for initiating the melting of said ice when formed to a predetermined thickness, said initiating means including a first sensing means mounted at a predetermined distance from said surface and periodically movable with respect to said surface to detect changes in the thickness of said ice for enabling operation of said initiating means when said ice has formed to said predetermined thickness, means to terminate said ice-melting-action including a second sensing means having a portion positioned in a predetermined relationship with respect to some ice located near said surface, force-producing means activated by said initiating means upon starting said melting action and disposed to act on said second sensing means for causing same to abut against said last-named ice and gradually move therewith as said ice progressively melts.

13. In a control device for a mechanism associated with apparatus having a surface subject to the formation of a solid but meltable material adjacent thereto, the combination of, control means for regulating the thickness of said material, actuating means adapted to provide an actuating force to operate said control means, sensing means having a portion positioned at a predetermined distance from said surface and disposed to move toward and away from said surface in response to movements of said actuating means and in relation thereto for precluding same from operating said control means when the thickness of said material formation is less than said predetermined distance, said sensing means including means for enabling said actuating means to be operatively connected to said control means for operation thereof after said material has formed to a thickness corresponding to said predetermined distance for blocking said movements of said sensing means.

19. In a control device for a refrigeration system subject to the formation of ice on a surface thereof, said refrigeration system including a source of energy normally supplied to said system, the combination of, control means for regulating the thickness of said ice, means directly sensing the thickness of said ice and powered by said energy to effect operation of said control means for automatically initiating the melting of said ice when formed to a predetermined thickness during ali conditions of operation of said system, and means to inactivate said control means including a second sensing means directly dependent on the melting of ice located near said surface to effect termination of said ice-melting action when substantially all said ice formed on said surface has melted.

2%. In a control device for a refrigeration machine subject to the formation of frost adjacent a surface therein, the combination of, control means for regulating the thickness of said frost, means to effect operation of said control means for initiating the melting of said frost when formed to a predetermined thickness, said initiating means including a first sensing means mounted at a predetermined distance from said surface and periodically movable with respect to said surface to detect changes in the thickness of said frost for enabling operation of said initiating means when said frost has formed to substantially said predetermined thickness, means to terminate said frost-melting-action comprising, a freezable liquid supported by means fixed in relation to a portion of said machine, a second sensing means including an element positioned in a predetermined relationship with respect to said freezable liquid, force-producing means activated by said initiating means upon starting said melting action and disposed to act on said element for causing same to abut against said liquid when frozen and gradually move therewith as said liquid progressively melts, and means to cause said frost-melting action to cease after a predetermined travel of said element, whereby the cycle can be repeated.

21. In a control device for a refrigerating machine hav ing a surface subject to the formation of frost thereon, the combination of, control means for regulating the thickness of said frost forming on said surface, means to effect operation of said control means for initiating the melting of said frost when formed 'to a predetermined thickness on said surface, said initiating means including a first sensing means mounted at a predetermined distance from said surface and periodically movable with respect to said surface to detect changes in the thickness of said frost for enabling operation of said initiating means when said frost has formed to said predetermined thickness, means to terminate said frost-melting action including a body of freezable liquid positioned in definite relation to a fixed portion of said refrigerating machine, termination sensing means including a termination sensing member disposed to abut said body of frozen liquid and normally disconnected from said control means, means to connect said control means to said termination sensing member upon operation of said initiating means when initiating said frost melting action, abutment means associated with said fixed portion, force producing means to cause said then-connected sensing member to abut against the'unmelted frozen liquid tending to compress same against said abutment means and to cause said member to move gradually a predetermined distance while held against the unmelted portion of said frozen-liquid by said force-producing means as said frozen liquid gradually melts, and means to effect a disengagement of said sensing member and said control means after movement of said member to said predetermined distance for terminating said defrosting action, whereby the elements and means return to their initial positions and the cycle can be repeated,

22. In a control device for a refrigerating machine'having a surface subject to the formation of frost thereon, the combination of, control means for regulating the thickness of said frost, actuating means periodically movable and disposed to operate said control means, initiation sensing means dependent on the formation of said frost and including a sensing element movable toward and away from said surface in response to said periodic movements of said actuating means to preclude said actuating means from operating said control means at least in one position of said element when said frost thickness is less than a predetermined amount, saidsensing element in a second position thereof including means to enable said actuating means to effect operation of said control means after the said frost has formed to substantially said predetermined amount for initiating the melting of said frost, means to terminate said frost-melting action including a vessel containing a freezable liquid positioned in definite relation to a fixed portion of said refrigerating machine, termination sensing means including a sensing member disposed to abut at least a portion of said body of frozen liquid in said vessel and normally disengaged from said control means, means to connect said control means to said sensing member upon operation of said initiating means when initiating said frost-melting action, biasing means to cause said then-connected sensing member to abut against the unmelted frozen liquid tending to compress same against a wall of said vessel and to cause said member to move gradually a predetermined distance while held against the unmelted portion of said frozen-liquid by said biasing means as same gradually melts, means to effect a disengagement of said sensing member and said control means after movement of said member to said predetermined distance for terminating said defrosting action, said biasing means then returning said control means to its original position corresponding to normal operation of said machine for terminating said frost-melting action, and means to simultaneously return said sensing member upon said disengagement to its original position, whereby the cycle can be repeated.

23. In a defroster control device for a refrigerating machine having a cooling unit subject to the formation of frost thereon and including normally inactive defrosting means to effect a melting of said frost, the combination of, control means to initiate intermittently operation of said defrosting means for melting said frost after same forms to an undesirable amount, means to terminate said frost-melting action when substantially all said frost has melted, said terminating means including an initially empty vessel positioned in definite relation to a fixed portion of said refrigerating machine, said terminating means also including sensing means having a first portion disposed within said frost and a second portion disposed within said vessel, biasing means to cause said first portion of said sensing means to abut against said frost tending to compress same against a fixed abutment associated with said machine and to cause said sensing means to move gradually a predetermined distance during a first defrosting cycle while held against the unmelted portion of said frost by said biasing means as said frost gradually melts to cause a first termination of said first defrosting cycle, said vessel being mounted to be in the flow path of said melting frost which re-freezes to ice for partially filling said vessel after said first termination, and in subsequent defrosting cycles, said frost termination being repeated to progressively and automatically fill said vessel with ice to its operating level, said second portion of said sensing means being urged by said biasing means to abut said ice simultaneously with said frost-abutting action by said first portion to establish the amount of said predetermined distance, whereby said termination at said operating level of ice depends on both said frost and said ice while abutted by said sensing means.

24. In a control device for a refrigerating machine having a surface subject to the formation of frost thereon, the combination of, control means for regulating the thickness of said frost, actuating means periodically movable and disposed to operate said control means, initiation sensing means dependent on the formation of said frost and including a sensing element movable in response to said periodic movements of said actuating means to preclude said actuating means from operating said control means at least in one position of said element when said frost thickness is less than a predetermined amount, said sensing element in a second position thereof including means to enable said actuating means to effect operation of said control means after the said frost has formed to substantially said predetermined amount for initiating the melting of said frost, means to terminate said frost-melting action when substantially all said frost has melted, said terminating means including an initially empty vessel positioned in definite relation to a fixed portion of said refrigerating machine, said terminating means also including termination sensing means having a first portion disposed Within said frost and a second portion disposed within said vessel, biasing means to cause said first portion of said termination sensing means to abut against said frost tending to compress same against a fixed abutment associated with said machine and to cause said termination sensing means to move gradually a predetermined distance during a first defrosting cycle while held against the unmelted portion of said frost by said biasing means as said frost gradually melts to cause a first termination of said first defrosting cycle, said vessel being mounted to be in the fiow path of said melting frost which re-freezes to ice for partially filling said vessel after said first termination, and in subsequent defrosting cycles said frost termination being repeated to progressively and automatically fill said vessel with ice to its operating level, said second portion of said termination sensing means being urged by said biasing means to abut said ice simultaneously with said frost-abutting action by said first portion to establish the amount of said predetermined distance, whereby said termination at said operating level of ice depends on both said frost and said ice while abutted by said termination sensing means.

25. In a defroster control device for a refrigerating machine having a cooling unit subject to the formation of frost thereon and including normally inactive defrosting means to effect a melting of said frost, the combination of, control means to initiate intermittently operation of said defrosting means for melt-ing said frost after same forms to an undesirable thickness, means assoclated with said control means to terminate said frost-melting action when substantially all said frost has melted, said terminating means including sensing means having a portion disposed so that said frost forms adjacent thereto, biasing means to cause said sensing means to abut against said frost tending to compress same against a fixed abutment associated with said machine and to cause said sensing mean-s to move gradually a predetermined distance while held against the unmelted portion of said frost by said biasing means as said frost gradually melts to cause a termination of said defnosting means operation.

26. In a control device for apparatus having a surface subject to the formation of frost adjacent thereto, the combination of; control means for regulating the thickness of said frost, a sensing member having a portion positioned near said surface for enabling frost to form adjacent said member and normally disconnected from said control means, means to actuate said control means and to operatively connect said control means to said sensing member for initiating a melting action of said frost, biasing means to cause said then-connected sensing member to abut against said frost and gradually move therewith as said frost progressively melts, and means to effect a disengagement of said connection after said frost has melted a predetermined amount for terminating said frost-melting action.

27. In a control device for a refrigerating machine having a surface subject to the formation of frost thereon, the combination of, control means for regulating the thickness of said frost, actuating means periodically movable and disposed to operate said control means, initiation sensing means dependent on the formation of said frost and including a sensing element movable in response to said periodic movements of said actuating means to preclude said actuating means from operating said control means at least in one position of said element when said frost thickness is less than a predetermined amount, said sensing element in a second position thereof including means to enable said actuating means to effect operation of said control means after the said frost has formed to substantially said predetermined amount for initiating the melting of said frost, termination sensing means including a sensing member disposed to abut at least a portion of said frost and normally disengaged from said control means, means to connect said control means to said sensing member upon operation of said initiating means when initiating said frost-melting action, biasing means to cause said then-connected sensing member to abut against the unmelted frost to compress same against a fixed abutment associated with said machine and to cause said member to move gradually a predetermined distance While held against the unmelted portion of said frost by said biasing means as said fnost gradually melts, and means to effect a disengagement of said sensing memher and said control means after movement of said member to said predetermined distance for terminating said defrosting action, whereby the elements and means return to their initial positions and the cycle can be re peated.

28. In a control device associated with apparatus having a surface subject .to the formation of ice adjacent thereto, the combination of; control means for regulating the amount of said ice, actuating means including a pcriodically movable element normally standing in a first position and adapted to directly operate said control means when moved from said first position, sensing means for detecting the quantity of said ice and movable in relation to said element and in response to movements thereof before said sensing means abuts said ice for precluding said actuating means from operating said control means when said ice formation is less than a predetermined amount, said sensing means including means to abut said ice after said relative movements for progressively reducing said movement as said ice forms to enable said movable element to be operatively connected to said control means for operation thereof after said ice has formed to substantially said predetermined amount to effect a melting of at least a portion of said ice, means for terminating said melting action of said control means after said ice formation has been reduced, and means to return said movable element to said first position.

29. In a control device for a' mechanism associated with a substantially solid but meltable material formed on a surface and subject to changes in the thickness thereof, the combination of; control means for effecting a change in the thickness of said material, actuating means including a movable actuating member normally disconnected from said control means but adapted to provide an actuating force to operate said control means, sensing means having a portion positioned at a predetermined distance from said surface and movable toward and away therefrom in response to said movements of said actuating member and relative thereto when said material has formed to less than a predetermined thickness to preclude said actuating member from operating said control means, means providing a force separate and independent of said actuating force and acting on said sensing means to effect said relative movements of said portion, and said sensing means including means for enabling said actuating member to be operatively connected to said control means for operation thereof upon formation of said material to said predetermined thickness to block said relative movements of said sensing portion, for initiating a change in the thickness of said material.

3%. In a control device for a mechanism associated with a substantially solid but meltable material formed on a surface and subject to changes in the thickness thereof, the combination of; control means for effecting a change in the thickness of said material, actuating means adapted to occasionally operate said control means and including an element intermittently movable away from a first position, sensing means having a portion positioned at a predetermined distance from said surface and movable toward and away therefrom in relation to and in response to said intermittent movements of said element into a second position thereof when said material has formed to less than a predetermined thickness, said sensing means including means to preclude said element from operating said control means upon said corresponding relative movement of said sensing means and said element, said sensing means also including means for enabling said element to be operatively connected to said control means for operation thereof at the first of said intermittent movements of said element following formation of said material to said predetermined thickness to substantially block said movements of said sensing portion, for causing a reduc tion in the thickness of said material, and means to return said element to said first position.

31. In a control device for a mechanism associated with apparatus having a surface subject to the formation of a substantially solid but meltable material adjacent thereto, the combination of; control means for regulating the thickness of said material, actuating means adapted to provide an actuating force to operate said control means, sensing means having a portion positioned at a predetermined distance from said surface and disposed to move in response to movements of said actuating means and in relation thereto for precluding same from operating said control means when the thickness of said material formation is less than said predetermined corresponding distance, said sensing means including means for enabling said actuating means to be operatively connected to said control means for operation thereof after said material has formed to said thickness corresponding substantially to said predetermined distance for blocking said movements of said sensing means, and cam means operatively associated with said actuating means and said sensing means to cause said relative movements thereof in response to said movement of said actuating means.

32. In a control device for a mechanism having a surface subject to the formation thereon of a solid but meltable material, the combination of; control means for effecting a change in the thickness of said material forming on said surface, actuating means adapted to occasionally operate said control means and including an intermittently movable element, sensing means having a portion movable toward and away from said surface in movements relative to said element in response to said intermittent movements thereof when said material has formed to an amount less than a predetermined thickness, cam means including a pair of cam-acting portions operatively associated with said element and said sensing means, said element including a first of said cam-acting portions and said sensing means including the second said cam-acting portion to cooperate with and to follow movements of said first cam-acting portion for causing said relative movements of said sensing means in response to said movements of said element only when said material has formed to an amount less than said predetermined thickness, means operatively associated with said sensing means to preclude said element from operating said control means upon said corresponding relative movement of said element and said sensing means, said sensing means portion being disposed to abut said material, said sensing means being blocked by said material upon said abutment for precluding said relative movement when said material has formed to said predetermined thickness by preventing said second cam-acting portion from following said first cam-acting portion, said precluding means during said blocking ac-- tion being disposed to enable said element to be operatively connected to said control means for operation thereof at the first of said intermittent movements of said element following formation of said material to said predetermined thickness for effecting a reduction in the thickness of said material.

33. In a defroster control device for a refrigerating machine having a cooling unit subject to the formation of frost thereon and including normally inactive defrosting means to effect a melting of said frost, the combination of; control means to activate intermittently said defrosting means for melting said frost, means to inactivate said defrosting means when substantially all said frost is melted, said inactivating means including sensing means having a part immersed within a vessel of ice fixed in relation to said machine, force-producing means to cause said immersed sensing part to abut against said ice tending to compress same against a wall of said vessel and to cause said part to move gradually with said ice at predetermined distance upon progressive melting of said ice to effect inactivation of said defrosting action, said vessel including a portion thereof located in relation to said cooling unit to be in the flow path of said melting frost, said sensing means including means disposed within said frost forming on said cooling unit to cause partial defrosting of said unit when first operating said machine to effect a gradual filling of said vessel.

34. In a control device associated with a refrigeration machine having a surface subject to the formation of frost thereon, the combination of; means to control the amount of said frost forming on said surface, actuating. means disposed to cause operation of said control means after said frost 'has formed to a predetermined amount, initiation sensing means dependent on the formation of said frost to preclude said actuating means from operating said control means when said formation of said frost is less than said predetermined amount, said sensing means including means to enable said actuating means to be operatively connected to said control means for operation thereof after said frost has formed to substantially said predetermined amount for initiating a melting of said frost, a vessel of ice fixed in relation to said machine, termination sensing means having a part immersed within said vessel, force-producing means to cause said immersed sensing part to abut against said ice tending to compress same against a wall of said vessel and to cause said part to move gradually with said ice a predetermined distance upon progressive melting of said ice to effect termination of said frost-melting action, said vessel including a portion thereof located in relation to said surface to be in the flow path of said melting frost, said sensing means including another portion disposed within said frost forming on said surface to cause partial defrosting of said surface When first operating said machine to effect a gradual filling of said vessel.

35. In a control device associated with apparatus having a surface subject to the formation of frozen substance adjacent thereto, the combination of; means to control the amount of said frozen substance, actuating means movable completely independent of said control means during one condition of said substance but adapted to operate said control means during a second condition of said substance, sensing 'means dependent on the formation of said frozen substance to preclude said actuating means from operating said control means in said first-named condition when said formation of said frozen substance is less than a predetermined amount, said sensing means including movable means to enable said actuating means to be operatively connected to said control means for operation thereof in said second-named condition after said frozen substance has formed to substantially said predetermined amount.

36. In a control device associated with apparatus having a surface subject to the formation of frozen substance adjacent thereto, the combination of; means to control the amount of said frozen substance, actuating means movable completely independent of said control means during one condition of said substance but adapted to operate said control means during a second condition of said substance, sensing means dependent on the formation of said frozen substance and including a sensing element movable in response to movement of said actuating means to preclude said actuating means from operating said control means at least in one position of said element in said first-named condition when said formation of said frozen substance is less than a predetermined amount, said sensing element at a second position thereof enabling said actuating means to be operatively connected to said control means for operation thereof in said second-named condition after said frozen substance has formed to substantially said predetermined amount.

37. In a control device for a mechanism associated with a meltable material subject to changes in the condition thereof, the combination of; control means for effecting a change in the condition of said material, actuating means movable completely independent of said control means during one condition of said material but adapted to operate said control means during a second condition of said material, sensing means having a portion positioned in a predetermined relationship with respect to said material and movable with respect thereto in response to said movements of said actuating means at said firstnamed one condition of said material, said sensing means enabling said actuating means to be operatively connected to said control means for operation thereof upon a change in said material to said second-named condition thereof causing said material to block said movements of said portion of said sensing means.

38. In a control device for a' mechanism associated with a meltable material subject to changes in the condition thereof, the combination of; control means for effecting a change in the condition of said material, actuating means including an intermittently movable element adapted to transmit a force for operating said control means, sensing means having a portion positioned in a predetermined relationship with respect to said material and movable relative thereto into periodic contact therewith in response to said intermittent movements of said element at one condition of said material, said portion of said sensing means being disposed to apply a force on said material during said periodic contacts which is less than said force of said element, said sensing means including means to prevent said element from operating said control means upon said corresponding relative movement of said sensing means, said sensing means enabling said element to be operatively connected to said control means for said periodic operation thereof at the first of said intermittent movements of said element following a sufficient change in said condition of said material to substantially block said movements of said portion of said sensing means.

39. In a control device for a mechanism having a surface subject to the formation thereon of a solid but meltable material, the combination of; control means for effecting a change in the thickness of said material forming on said surface, actuating means adapted to occasionally operate said control means and including an intermittently movable element, sensing means having a portion movable toward and away from said surface in movements relative to said element in response to said intermittent movements thereof when said material has formed to an amount less than a predetermined thickness, means operatively associated with said sensing means to preclude said element from operating said control means upon said corresponding relative movement of said element and said sensing means, said sensing means being disposed to abut said material when formed to said predetermined thickness to block said movement of said sensing means for preventing said relative movement thereof, said precluding means during said blocking action being disposed to enable said element to be operatively connected to said control means for operation thereof at the first of said intermittent movements of said element following formation of said material to said predetermined thickness, for effecting a reduction in the thickness of said material.

40. In a defroster control device for a refrigerating machine having a cooling unit subject to the formation of frost thereon and including normally inactive defrosting means to effect a melting of said frost, control means to activate intermittently said defrosting means for melting said frost, means to inactivate said defrosting means when substantially all said frost is melted, a body of frozen liquid fixed in relation to said machine, said inactivating means including sensing means having a part adapted to operatively engage said body of frozen liquid, forceproducing means to cause said sensing part to abut against said frozen liquid tending to compress same against a fixed portion of said refrigerating machine and to cause said part to move gradually with said frozen liquid a predetermined distance upon progressive melting of said frozen liquid to effect inactivation of said defrosting means, whereby said body of frozen liquid acts as a thermally varying frozen-liquid link between said sensing part and the fixed portion of said refrigerating machine, and initiating means for said defrosting means adapted to connect said control means to said sensing means after a predetermined amount of frost has formed on said cooling unit to effect said activation of said defrosting means.

41. In a control device associated with a refrigeration machine having a surface subject to the formation of frost thereon, the combination of; means to control the quantity of said frost forming on said surface, actuating means disposed to cause operation of said control means after said frost has formed to a predetermined dimension, initiation sensing means dependent on the formation of said frost to preclude said actuating means from operating said control means when said formation of said frost is less than said predetermined dimension, said sensing means including means to enable said actuating means to be operatively connected to said control means for operation thereof after said frost has formed to substantially said predetermined dimension for initiating a melting of said frost, a vessel of ice fixed in relation to said machine, a termination sensing member having a portion disposed adjacent a body of frozen liquid in said refrigerating machine and disconnected from said control means during normal operation of said machine, means to operatively connect said control means to said sensing member for initiating said defrosting action, biasing means acting on said control means to cause said then-connected sensing member to abut against the frozen liquid tending to compress same between said sensing member and a-fixed part of said machine and to move therewith as said frozen liquid progressively melts, to form a thermally-varying frozenliquid link between said sensing member and said part to sustain said defrosting action, means to efiect a disengagement of said connection after a predetermined travel of said sensing member during said last-named movement, said biasing means then returning said control means to its original position corresponding to said normal operation of said machine for terminating said defrosting action, and means to return said sensing member upon said disengagement to its original position, whereby the cycle may be repeated.

42. In a control device associated with refrigeration apparatus having a surface subject to the formation of frost adjacent thereto, the combination of; means to control said amount of said frost forming on said surface, actuating means adapted to provide a force to operate said control means, initiation sensing means dependent on the bulk formation of said frost to a predetermined amount to enable said actuating means to operate said control means only after the said frost has formed to said predetermined amount for initiating a melting thereof, and termination sensing means operatively associated with said control means to determine the duration of said melting of frost, said termination sensing means including a movable element adapted to abut a portion of said frost to compress same against fixed stop means associated with said refrigeration apparatus for terminating said melting action when said element has traveled a predetermined distance.

43. In a control device associated with apparatus having a surface subject to the formation of a meltable and freezeable material adjacent thereto, the combination of; means to control the thickness of said material forming on said surface, actuating means movable periodically completely independent of said control means during one thickness of said material but adapted to operate said control means during a second thickness of said material, sensing means to measure the thickness of said material and intermittently movable wtih respect to said surface in response and corresponding to said periodic movements in said first-named thickness whenever said material has formed less than a predetermined thickness thereon, said movements of said sensing means being substantially prevented by the bulk of said material upon formation thereof to said predetermined amount in said second-named condition to enable actuation of said control means by said actuat ng means.

44. In a control device for a mechanism having a surface subject to the formation thereon of a freezable and meltable material, the combination of; control means for effecting a change in the thickness of said material accumulated on said surface, initiating means adapted to provide a relatively large actuating force for periodic operation of said control means when said material has accumulated to a predetermined thickness, thickness-sensing means operable to detect the accumulation of said material on said surface to said predetermined thickness for enabling the transmission of said actuating force to operate said control means upon operation of said initiating means, and means producing a sensing force considerably less in magnitude than and independent of said actuating force to cause said detecting operation of said sensmg means.

45. In a defroster control device for a refrigerating machine having a cooling unit subject to the formation of frost thereon and including normally inactive defrosting means to effect a melting of said frost, the combination of; control means to activate intermittently said defrosting means for melting said frost, means to inactivate said defrosting means when substantially all said frost is melted, said inactivating means including ice-sensing means having a part immersed within a vessel of ice fixed in relation to said machine, force-producing means to cause said immersed sensing part to abut against said ice tending to compress same against a Wall of said vessel and to cause said part to move gradually with said ice a predetermined distance upon progressive melting of said ice to effect inactivation of said defrosting action, said vessel including a portion thereof located in relation to said cooling unit to be in the flow path of said melting frost, a frost-sensing element operatively connected to said ice-sensing means for movement therewith and disposed to abut said frost forming on said cooling unit to cause partial defrosting of said unit when first operating said machine for enabling q as said melted frost to gradually fill said vessel in succeeding defrosting cycles.

References Cited by the Examiner UNITED STATES PATENTS 2,624,180 1/1953 Grimshaw 62140 2,704,441 3/1955 Morton 62140 2,867,092 1/1959 Perry 62-140 10 ROBERT A. OLEARY, Primary Examiner.

W. E. WAYNER, Assistant Examiner. 

1. IN A CONTROL DEVICE ASSOCIATED WITH APPARATUS HAVING A SURFACE SUBJECT TO THE FORMATION OF ICE ADJACENT THERETO, CONTROL MEANS FOR REGULATING THE AMOUNT OF SAID ICE, ACTUATING MEANS ADAPTED TO OPERATE SAID CONTROL MEANS, SENSING MEANS DIRECTLY DEPENDENT ON THE FORMATION OF SAID ICE AND DISPOSED TO MOVE INTO THE PATH OF TRAVEL OF SAID ACTUATING MEANS TO BLOCK SAME FROM OPERATING SAID CONTROL MEANS WHEN SAID ICE FORMATION IS LESS THAN A PREDETERMINED AMOUNT, SAID SENSING MEANS INCLUDING MEANS DISPOSED TO ABUT SAID ICE FOR PREVENTING SAID BLOCKING MOVEMENTS OF SAID SENSING MEANS TO ENABLE SAID ACTUATING MEANS TO BE OPERATIVELY CONNECTED MECHANICALLY TO SAID CONTROL MEANS FOR OPERATION THEREOF AFTER THE SAID HAS FORMED TO SUB- 